1. Field of the Invention
The present invention relates to a retractable lens system that comprises a slidable lens retracting device with which at least one optical element of the retractable lens system slides off an optical axis of the lens system when the retractable lens is retracted.
2. Description of Prior Art
Retractable lens systems are commonly applied in cameras or other optical devices for reducing the overall size of a camera in a non-photographing condition. The camera incorporating the retractable lens has the advantages of compactness and improved portability. Conventionally, a retractable lens comprises a plurality of optical elements, such as lenses, of which one or more optical elements are movable along a common optical axis for retraction. Therefore, as shown in FIG. 1, when such a retractable lens system is fully retracted, all the optical elements or lenses are stacked along the optical axis and the minimum overall length of the lens system that can be achieved along the optical axis in the retracted condition is at least equal to the sum of the thicknesses of all the optical elements. It is impossible to make the overall retracted length of the retractable lens system smaller than the sum of the thicknesses of all the optical elements. Accordingly, there is no way to further reduce the overall size of a camera employing such a conventional retractable lens system.
U.S. Patent No. 2006045517 discloses a retractable lens camera including a displacing unit. At least two lens groups are swung and displaced by the displacing unit to an escaping space off an optical axis for minimizing the retractable lens. However, swinging of the lens groups into/off the optical axis makes the operation and assembling of the lens groups unstable, often leading to damage thereof. Further, structural instability may also be resulted in other parts of a camera that employs such a retractable lens due to swinging of the optical elements.
U.S. Pat. No. 6,031,998 discloses a digital camera comprising at least two lens groups of which a rearmost lens group is movable out of a photographing light path by an image pickup unit moving device swinging in a non-photographing condition of the digital camera. The rearmost lens group can move back into the photographing light path in a photographing condition. For the same reasons stated above, the rearmost lens group is likely to be subjected to the instability problem and such as problem leads to deterioration of quality and operation of the camera.
Accordingly, to overcome the problems present in the known techniques, it is desired to provide a retracting device that effectively reduces the overall size of a compact retractable lens in a non-operational condition, while maintaining a stable structure and good optical quality.